Benito comments on Open thread for December 17-23, 2013 - Less Wrong

5 Post author: ciphergoth 17 December 2013 08:45PM

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Comment author: Anatoly_Vorobey 18 December 2013 12:10:30AM 15 points [-]

Yesterday I noticed a mistake in my reasoning that seems to be due to a cognitive bias, and I wonder how widespread or studied it is, or if it has a name - I can't think of an obvious candidate.

I was leaving work, and I entered the parking elevator in the lobby and pressed the button for floor -4. Three people entered after me - call them A, B and C - but because I hadn't yet turned around to face the door, as elevator etiquette requires, I didn't see which one of them pressed which button. As I turned around and the doors started to close, I saw that -2 and -3 were lit in addition to my -4. So, three floors and four people, means two people will come out on one of the floors, and I wondered which one it'll be.

The elevator stopped at floor -2. A and B got out. Well, I thought, so C is headed for -3, and I for -4 alone. As the doors were closing, B rushed back and squeezed through them. I realized she didn't want -2, and went out of the elevator absent-mindedly. I wondered which floor she did want. The elevator went down to -3. The doors opened and B got out... and then something weird happened: C didn't. I was surprised. Something wasn't right in my idle deductions. I figured it out in the few seconds it took for the elevator to descend to my floor and let me out together with C.

Where did I go wrong? When I knew that B left on -2, I deduced, correctly, that C will get out on -3. But then B came back; the fact of her leaving on -2 turned out to be wrong; yet I didn't cancel my deduction about C and didn't return him the "freedom" of leaving either on -3 or on -4. It didn't even occur to me to do that. Why didn't it?

It seems important that the new information was a correction of a known fact, and not just some other fact. If I treat the new information "B does not leave at -2" purely as a fact, the consequence for C is "C may leave either on -3 or on -4", which is already clear as it is and not worth updating. No, it seems "B does not leave at -2" has a special character when it comes to correct the previously-assumed "B left at -2". It comes as a "rollback" of existing information and I need to "roll back" everything I deduced from that information. And that seems hard to do and easy to forget. So if wasn't just a failure to update that I committed. It was a failure to "roll back".

On reflection, this mistake seems like something we might be doing often, and something to keep an eye out for. Is there a name for this mistake, has it been studied?

Comment author: Benito 18 December 2013 11:09:29AM 4 points [-]

Seems related to the studies where people are told a fact, but it's in red, which they're told means it's not true. After seeing lots of different facts in colours blue or red (blue means true) they're asked about certain facts, and they're more likely to remember a false fact as true than a true fact as false - we're more likely to believe things, and don't tend to take on contrary evidence as easily.